Recently, home bleaching has been introduced into the dental health care market for the management of stained or discolored teeth. Such treatments are administered by application of bleaching products that are professionally prescribed and supervised, or purchased over the counter and self-administered.
In both the professional and over the counter markets, home bleaching is a technique utilizing oxidizing agents, such as carbamide peroxide or other peroxy compounds, which are delivered to the dental arch by the patient using a rigid dental appliance which is custom fabricated by a dentist or dental laboratory. Protocols supervised by dental professionals employing home bleaching generally have the patient apply a rigid custom dental appliance for periods of up to 120 minutes per day. The daily applications are administered over several weeks, thereby totaling between 20 to 40 hours of home bleaching time. Over the counter procedures typically call for reduced daily bleaching times of up to one hour, and vary in total treatment times.
The exact origin of home bleaching is unclear. The earliest reports of dental bleaching occurred in the mid-1960's when Glyoxide.TM., an over-the-counter preparation containing 10 percent carbamide peroxide in glycerin which was used for soft tissue wound healing (commercially available from Marion Merrel Dow, Inc.) was observed to have and used for the desirable side effect of whitening teeth. In 1972, Proxigel.TM. (commercially available from Reed & Carnrick Pharmacym), was introduced as the agent of choice for whitening teeth. Proxigel.TM. is a combination of water, glycerin, Carbopol.TM. (thickening agent) and 10% carbamide peroxide.
The first report of a home bleaching procedure was published in 1989, when Haywood and Heymann reported successful bleaching using Proxigel.TM. in a custom fabricated dental appliance to be worn at night. In the Haywood and Heymann procedure, the bleaching agent was placed in a soft plastic, vacuum-formed dental appliance for an average of 7.5 hours per night for 2 to 5 weeks. Also in 1989, a White and Brite.TM. bleaching agent (commercially available through Omni International) became the first system sold specifically for whitening teeth. White and Brite.TM. is a preparation contain ten per cent carbamide peroxide in glycerine, and is sold exclusively to dentists in conjunction with custom-fitted or prescription dental appliances. Since its introduction into the professional dental health care market, over 20 companies have marketed similar products.
Fabrication of rigid, custom dental appliances entails fabricating stone models of the patient's dental arch impressions, and heating and vacuum-forming a thermoplastic sheet corresponding to the stone models of a patient's dental arches. Thermoplastic films are sold in rigid or semi-rigid sheets, and are available in various sizes and thicknesses. Some manufacturers also may provide laminations of porous foams or low modulus plastics to the rigid thermoplastic films.
In the professional teeth bleaching market, dentists have traditionally utilized one of three types of dental appliances for delivery of home bleaching agents. All three are rigid and custom-fitted to an individual patient's dental arches. The first type is molded to closely fit a patient's dental arches, having no space or lining within the trough for inserting a dental arch.
The second type of rigid custom dental appliance is an "oversized" rigid custom dental appliance, wherein the facial surfaces of the teeth on the stone models are augmented with linings such as die spacers or light cured acrylics. In "oversized" appliances, thermoplastic sheeting is heated and subsequently vacuum formed around the augmented stone models of the dental arch.
The third type of rigid custom dental appliance, which is used with less frequency than the types of appliances described above, is a rigid bilaminated custom dental appliance fabricated from laminations of materials, ranging from soft porous foams to rigid, non-porous films. The non-porous, rigid thermoplastic shells of these bilaminated dental appliances encase and support an internal layer of soft, porous foam.
Professionally supervised bleaching systems utilizing each of these three varieties of custom-fitted appliances require at least two dental office visits and the fabrication of the rigid custom dental appliance. During the first office visit, the dentist explains the procedure, expected outcome and risks of side effects, and estimated costs of the professionally supervised dental bleaching. If the patient then wishes to proceed, dental impressions are taken and a second office visit is scheduled. During the interim period between the first and second office visits, a rigid custom-fitted dental appliance is fabricated from a thermoplastic sheet vacuum molded to a stone model of the patient's dental impressions. Subsequent to molding the appliance, the excess sheeting is removed and the resulting rigid, custom dental appliance polished and provided to the dentist for fitting to the patient's dental arches. If the patient elects to treat both upper and lower arches, a separate dental appliance for each arch must be fabricated.
At the second office visit, the dentist delivers the first bleaching treatment and instructs the patients on the proper procedure to dispense bleaching agent in the custom appliance. The dentist then provides to the patient a sufficient amount of carbamide peroxide gel to complete the home bleaching regimen prescribed. Typically, the dentist provides several syringes containing about 2 ml to 3 ml of 10 percent to 15 percent carbamide peroxide gel. The patient subsequently applies the bleaching agent daily or as the dentist otherwise prescribes. In the home dental care regimen, the patient dispenses the bleaching agent into the rigid custom dental appliance and then places the appliance over the dental arch for a specified period of time. Typically, the recommended treatment period ranges from 30 to 120 minutes per day. At the end of the treatment period, the dental appliance is removed, thoroughly cleaned to remove any remaining bleaching agent, and then stored until the next application.
Unfortunately, there exist many problems with existing dental bleaching agent treatment systems. As to systems utilizing rigid custom-fabricated dental appliances, the time and expense of forming dental impressions, making the dental appliances and associated dental laboratory work, and multiple office visits are costly and time consuming. Moreover, if a dental appliance is improperly fitted or otherwise defective, a patient may be further inconvenienced by the requirement of additional office visits may be required.
Problems with existing dental treatment regimens are manifold. Conventional rigid, custom-fabricated dental appliances require time-consuming and expensive dentist office visits, dental laboratory tests and fitting of each patient's dentition. Furthermore, any changes in the surface of the patient's teeth, such as filings, crowns, and other accidental or therapeutic alterations of the dentition, would affect the fit of the rigid custom dental appliance and warrant repeating the entire fabrication procedure. Refabrication of the splint may also be required in the event of subsequent rebleaching.
There also exist particular drawbacks with custom bilaminated dental devices, including occlusion and retention of bleaching agent. Furthermore, cleaning and maintenance of foam-lined dental appliances may be problematic, due to the high surface area and pore volume of the foam materials.
Oversized rigid custom dental appliance also have particular drawbacks, including, but not limited to, occlusions in the augmented region, increased appliance fabrication time and cost irritation and the lip of the appliance contacting the gingival region, and decreased retention to the bleaching agent within the target area.
Such and other problems triggered the development of an alternative type of treatment regimen employing self-administered dental bleaching replacing rigid custom dental appliances with disposable soft universal fit, U-shaped appliances. Soft open cell foam trays saturated with a premeasured quantity of bleaching agent (distributed through Cadco Dental Products in Oxnard, Calif. under the tradename VitalWhite.TM.). Recommended treatment protocol described in the product's package insert instructs the patient to fit the device around his or her teeth and to keep the tray in position for sixty minutes after which time it is removed and discarded. Cadco recommends delivery of fourteen sixty-minute applications in a two week period.
Unfortunately, however, side effects of foam appliances used in home bleaching systems have also presented their unique drawbacks. Such foam appliances fail to direct and confine the application of home bleaching agents on the surfaces of a patient's teeth, which is critical to the safety and efficacy of any dental appliance, or other medical device used in or on the human body. Furthermore, the surfaces of such foam devices, which are saturated with bleaching agent are open and exposed to the oral cavity, and allow the elution of large quantities of bleaching agent from the device, enter the oral cavity, and be ingested by the patient. In addition, because of the discomfort associated with the moisture buildup resulting from foaming of the bleaching agent and salivation, patient compliance and acceptance is low.
Such disadvantages include, but are not limited to, the bulk of foam trays of such systems, lack of adequate structural rigidity to fit securely over the dental arches, excessive salivation, and consequent adverse side effects, including hypersensitive reactions and nausea. The likelihood of such side effects is commensurably increases with the strength of the bleaching agent concentration, and is more likely if a patient is unaccustomed to teeth bleaching.
To date, no medicinal agents have been derived to alleviate or attenuate such and other contraindications. Nor have compositions been derived to general, improve the condition of the teeth and mouth, regardless of whether the dentition have been subject to whitening or another dental procedure. Thus, there exist many problems with devices for delivery of home bleaching agents which are presently available.
Additional drawbacks with known systems for treatment of dental arches relate to improper dispensation of agents into dental appliances, particularly when the agents are dispensed by patients who are inexperienced and unaware of the importance of precision and infection control. Improper dispensing may result in overfilling, spillage or incorrect measurement of the agent. Lack of aseptic technique increases the risk of contaminating the bleaching or other medicinal agent into an appliance. Patients who self-administer bleaching or other medicinal agents often fail to provide the careful maintenance, cleaning, and storage which is necessary for a rigid custom dental appliance to perform adequately throughout its entire service life.
Further disadvantages of known bleaching systems relate to dispensing of excessive bleaching or other medicinal agent into the dental appliance which is subsequently displaced from the appliance into the oral cavity, spilled into the mouth, and ingested. Ingestion of significant amounts of bleaching agent may cause the user great discomfort and hypersensitive reactions. The excessive bleaching agent may also cause gingival irritation, burning, edema, nausea and other allergic reactions. A patient may thus ingest The risk of such side effects excessive quantities of bleaching agent increases with the number of treatments, and becomes most significant after the multiple treatments typically required to attain acceptable clinical results. The sponge-like permeability of disposable foam trays merely exacerbates-problems of systems utilizing custom dental appliances resulting from their poor retention or confinement of the bleaching agent to the target area.
Some of the above problems were addressed by the single-step, single use dental appliance and method described in U.S. Pat. No. 5,575,654, a predecessor to the present application. The latter system addresses problems resulting from leakage and hygiene discussed above by utilizing a prefabricated U-shaped dental appliance composed of a nonporous polymer that has a front and rear wall integrally joined at their lower edges to form a trough. As claimed, a predetermined amount of bleaching agent is predispensed in its trough. A layer of open cell foam is preferably affixed to the front and rear walls of the latter appliance.
Although the latter system addressed significant drawbacks relating to leakage and spillage, limitations of this predispensed, prepackaged, single-step dental treatment procedure persist. A particular limitation involves the reduced shelf life and associated efficacy of existing bleaching agents, particularly when predispensed in an appliance. Over a limited period of time, the efficacy of the agent may be attenuated primarily due to moisture in the agent or the surrounding air.
Currently available bleaching agents utilized in both the professional and over the counter markets are either viscous liquids or gels. The peroxy compounds are hydrous and typically provided in gel matrices of differing concentrations. Carbamide peroxide gels dispensed in the professional market range between about 10 to 25 percent while the concentration of carbamide peroxide in over the counter products range between about 6 and 15 percent. Bleaching agents are commercially available and packaged in separate dispensing containers such as bottles and tubes, and most often, gels. The peroxy compounds utilized in the professional and over the counter markets are hydrated and generally provided in gel matrices differing in concentration. Carbamide peroxide gels dispensed in the professional market range between about 10 and 25 percent, while the concentration of carbamide peroxide in over the counter products range between about 6 and 15 percent. When applied at home, the patient dispenses an estimated quantity of bleaching agent to the rigid custom dental appliance, and then places the appliance over the dental arches being treated.
Existing carbamide peroxide systems utilize gels comprising hydrogen peroxide coupled to urea in either anhydrous glycerin base or a soluble, aqueous Carbopol base. When carbamide peroxide is hydrated, the hydrogen peroxide breaks down into urea and peroxide, which subsequently breaks down into water and oxygen. This instability of the agent in hydrated form limits the efficacy of existing bleaching agents, particularly when exposed to water.
This background is not an exhaustive discussion of problems with prior art bleaching systems, but merely exemplifies some prevalent drawbacks encountered with present devices. Therefore, it is apparent that there is a need for substantial improvement in dental treatments involving application of bleach or other medicinal agents to a patient's dentition and periodontal tissue.